Abstract: GNSS suppressive jamming is a critical technique in navigation countermeasures. Accurately evaluating its coverage rate is essential for assessing jamming effectiveness and optimizing equipment performance. However, existing evaluation methods primarily rely on uniform sampling, which suffers from low efficiency due to overly dense sampling points and insufficient accuracy due to sparse sampling. To address these limitations, this study proposes a novel GNSS suppressive jamming coverage evaluation method based on an enhanced triangulated irregular network (TIN) that comprehensively accounts for terrain influences, jamming visibility, and interference distance. Experimental results demonstrate that compared to traditional approaches, the proposed method significantly reduces the number of grid sampling points while maintaining minimal deviation from the true coverage rate. This improvement markedly enhances evaluation efficiency and accuracy. In our experiments, this method ensured that the interference coverage assessment error was only 0.04% in flat areas while reducing the number of grid sampling points by about 2/3. In mountainous areas, the coverage error was 0.66% and the number of grids was reduced by nearly 8/9, effectively improving the efficiency of field assessment.